1. Field
The present invention relates to the field of controlling fluid flow and its rate in a micro assay device for the detection of a small quantity of an analyte in a fluid. More particularly, the present invention relates to a micro (thin film type) valve apparatus using a microbead to control fluid flow or its rate, and a method for controlling the micro valve apparatus.
2. Description of the Related Art
To date, for most diagnostic assay apparatuses for the detection of small quantities of analytes in fluids, multiple-sample preparation and automated reagent addition devices, or multiple-sample assay apparatuses for identifying a number of samples at the same time, either in parallel or serial procession, have been designed to improve efficiency and economy. Such an automated reagent preparation device and an automated multiple-sample assay apparatus are integrated into a single thin film type apparatus. This thin film type diagnostic assay apparatus can automatically or semi-automatically accurately analyze hundreds of analytes using trace amounts of a sample and reagents. The thin film type assay apparatus needs a valve for automatically supplying a sample or reagents (enzyme and buffer). However, designing such a valve for a thin film type assay apparatus is complicated. Therefore, there is a need to design a simple valve suitable for the thin film type assay apparatus.
<Thin Film Type CD & DVD>
The standard compact disk is formed from a 12-cm polycarbonate substrate, a reflective metal layer, and a protective lacquer coating. DVD stands for digital video disk, a type of optical disk of the same size as the compact disk, but with significantly greater recording capacity.
The polycarbonate substrate is optical-quality clear polycarbonate. In a standard pressed CD or DVD, the data layer is part of the polycarbonate substrate, and the data are impressed as a series of pits by a stamper during injection molding. In the injection molding process, melted polycarbonate is injected into a mold under high pressure and cooled in a mirror image of the mold or stamper. As a result, reverse pits of the stamper are formed on the polycarbonate disk surface during mastering as binary data. The stamping master is typically glass.
Those disks can be modified into CD-ROMs, DVDs, bio-CDs or bio-DVDs as thin disk type diagnostic assay apparatuses for detecting non-biological analytes or biological molecules in a fluid. In this case, during injection molding, instead of the pits, channels as fluid flow paths and chambers as buffer reservoirs can be formed in the disk surface. Additionally, a thin film type valve for controlling fluid flow and its rate through the channels formed in the thin disk surface is required.
GB 1075800 (published Jul. 12, 1967), entitled “Disc for Centrifuge”, disclosures a device for flowing a sample fluid supplied via an inject hole of the disc over the surface of the disc by centrifugal force. EP 3335946 (published Apr. 12, 1965), entitled “Separating Disks for Centrifuge”, discloses an apparatus for separating fluid samples injected via an inject hole of the disc by flowing the samples through channels or chambers formed in the disc. However, these apparatuses failed to overcome the problems of the thin film type valve and to precisely control flow rate.
A general valve using an electromagnet opens or closes a flow path using a cylinder or a plunger that is moved by magnetic force. To intensify the magnetic force so as to move the cylinder or flange, a ferroelectric core of an appropriate size and a number of wires wound around the core are required. Also, a large amount of electricity is required to turn on or off the valve and move the cylinder or flange. The valve using the electromagnet cannot be constructed as a thin film type valve due to the size of the electromagnet. The valve generates excess heat by consuming a large amount of electricity. To address these problems, according to the present invention, electromagnets and a microbead are used. A valve using the microbead according to the present invention can be constructed in thin film form, and a small force is required to move the microbead. Accordingly, the electromagnets can be formed as thin films. Also, since electricity consumption is very low, no heat is generated when the valve is operated.
Therefore, the micro (thin film type) valve apparatus and the method for controlling the same according to the present invention are suitable for a thin film type diagnostic assay apparatus, such as a lab-on-a-chip, or DNA-chip, for detecting a small quantity of an analyte in a fluid, and especially, for interconnecting and blocking channels formed in a thin disk type assay device, such as a CD-ROM, a DVD, a bio-CD, and a bio-DVD, or for controlling the rate of fluid flowing.
Accordingly, it is an object of the present invention is to provide a micro (thin film type) valve apparatus and a method for controlling the same, in which a microbead that is moved by the magnetic or electric force generated by electromagnets or electrode plates installed on the top and bottom surfaces of its body is placed in the middle of channels to block or interconnect the channels.
It is another object of the present invention to provide a thin film type diagnostic assay apparatus for detecting a small quantity of an analyte using the micro (thin film type) valve apparatus for controlling fluid flow and its rate, and particularly, to provide an nucleic acid assay apparatus and method for detecting whether a sample contains a target nucleic acid or not, using the micro (thin film type) valve apparatus.